A colony of young monkeys of the species Macaca fascicularis has been established in Hazleton Laboratories. They were inspected by a veterinary surgeon before being dispatched from Malaysia. They have been subjected to intensive quarantine procedures including tuberculin testing. Antibiotics such as tetracycline have been avoided. Pre-experimental samples of plaque have been obtained from all animals. Strep. mutans has not been found. The biochemical analysis of plaque suggest that its composition is similar to that found in man. The levels of serum immunoglobulins have been determined in all animals. Wide variations have been found. The animals have been divided into experimental groups on the basis of age and the levels of immunoglobulins. The monkeys are now on an experimental regimen.